underscore types in mpu.h

I am porting the eMD-6.12 to nRF52832 by NordicSemiconductor. Currently, I am trying to compile the stm32L arm project with a gcc toolchain via makefile. The compiler has no definition of the underscore types inside the mpu.h file: __u16, __u8, __u32, __s32, and the like. I see the __KERNEL__ and __LINUX__ branches to include ioctl. and types.h, but these files are not part of the eMD-6.12 package. I also see mltypes.h is included but have not seen a definition of the underscore types.
Question: how to include the definitions of the underscore types?